High Thermal Stability Polyurethane with Low Heat Generation

8 High Thermal Stability Polyurethane with Low Heat Generation 

It is well known that conventional polyester-based urethane elastomers extended with butanediol can withstand continuous use temperatures of about 80 °C. At higher temperatures, a reduction in the physical and mechanical properties is seen due to degradation of the material. The thermal stability of the polyurethanes is related to the nature of the starting materials such as the aromatic diisocyanate and diol chain extender. The hard segment of the urethane elastomer is primarily responsible for temperature resistance, and the soft segment determines the material s performance at low temperature. 

Butanediol chain extender has four aliphatic carbon atoms in the chain. On the other hand, HER is an aromatic diol chain extender with the following structure  

In order to demonstrate that HER compared to butanediol-based elastomer has better physical and mechanical properties at elevated temperatures, cast elastomers with 95% stoichiometry have been made from an MDI terminated polyester prepolymer (Baytec MS-242) extended with butanediol and HER-HP (from INDSPEC Chemical Corporation). Test specimens were cut from a sheet post cured at 110 °C for 16 hours, for the tensile, tear, DSC and DMA determinations. In the preparation of material for the dry heat aging evaluation, tensile, DSC and DMA samples were placed in an air oven with the temperature controlled within 2 °C of the set point and aged for 28 days at 100 °C, 21 days at 120 °C and 14 days at 135 °C. Then, all the samples were stored for at least seven days at room temperature and 50% relative humidity before testing. 

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